He has access to his basking spot. He is on it right now. I cleared the substrate out of his warm hide so that he could have access to warmth. So although my ambient temps need adjusting, he is able to warm himself up on his basking spot.

Any tips on increasing the ambient temp?

The UTH is under the Polythylene liner in the drawer. I have a temp gun that I use to measure his basking spot and some digital thermometers that measure ambient temp and humidity.